The present invention relates to a feeding and cutting device for sheet material in the form of a continuous web or ribbon to be cut into pieces of substantially equal length, each said piece being defined, on said web, by at least two prearranged transverse cuts or slits provided through a central portion of said web, and which are not long enough to sever the web.
The device of the invention is preferably to be used in combination with a wrapping machine for cigarette packets to provide labels or price and advertising coupons to be inserted between the inner tin-wrap and the outer wrap of individual packets, or to be applied on to the outer wrap of the same as well as of packages, such as cartoons, enclosing a plurality of cigarette packets. However, it is to be pointed out that the device of the invention is particularly suited to be used to provide individual cigarette packets with a respective label or coupon.
The feeding and cutting devices of the prior art, hereinafter referred to as "known devices", generally comprise a web path, along which the web is advanced by advancing means, and cutting means arranged along said path and normally comprising a stationary blade and a movable blade operating scissors-like to sever the web into pieces.
As far as the webs are concerned, it is to be pointed out that they are normally provided, at least on one side, with a series of prints each defining a label or coupon. Owing to unavoidable repetitive errors in the printing process, the spacing of the prints is substantially, but not exactly, constant.
The above made it necessary for the known devices to include registration means adapted to cooperate with reference marks provided on the web between adjacent prints, to register the position of the web along the web path to the cutting means so as to allow the latter to sever the web precisely at the gap or line separating adjacent prints.
U.S. Pat. No. 2,725,101 issued on Nov. 29, 1955 teaches how to provide a web consisting of a series of printed labels, with transverse slits formed through only a portion of the width of the web between adjacent labels; how to advance in a step-by-step manner said web along said web path by means of reciprocating advancing means so designed and arranged that, during each advancing stroke, the web is advanced a distance less than the length of a label; and how to register, at the end of each said advancing stroke, the position of the web so as to arrange a slit thereof on a plane at right angles to said web path and along which the cutting means operate.
The above registration is carried out by means of a registering member which is arranged at a distance upstream from the cutting means and engages the web to depress a central portion thereof arranged immediately upstream from a slit, thus causing the trailing edge of said slit to be depressed without substantially deforming the leading edge thereof.
The registering member is then advanced a predetermined length to engage said leading edge and to advance the web, the advancing stroke of the registering member being such that, at the end of it, a slit arranged downstream from the said slit engaged by the registering member, finds itself exactly on the aforementioned cutting plane. Of course, the above occurs provided that the labels comprised between the slit engaged by the registering member and the slit along which the cutting means would operate are all as they are supposed to be, that is of equal length. As already said, the above might be not true owing to errors during printing; accordingly, in the device subject of U.S. Pat. No. 2,725,101, some of the cut may not coincide exactly with a respective slit. It is true however that, owing to the registering member, any cutting error will not affect the following cutting operations. U.S. Pat. No. 2,885,839 issued May 12, 1959 teaches that if a ribbon provided with spaced registration transverse slits is to be severed by cutting means exactly at said registration slits independently of the distance between successive registration slits, the best way of operation is that of first bringing each said slit into engagement with the cutting means, and then operating the cutting means.
In other words, U.S. Pat. No. 2,885,839 teaches that if a ribbon provided with preformed spaced transverse slits is to be severed into pieces exactly along said slits by a cutting means, the more suitable registering member to be used is the cutting means itself.
A registering cutting means is disclosed in U.S. Pat. No. 3,435,717 issued Apr. 1, 1969 and relating to an apparatus for cutting labels from a continuous ribbon of labels comprising at least one cut between adjacent labels, and for supplying the separate cut labels to a labelling or banding device.
In the above apparatus, registration is accomplished by engaging the ribbon and deform the same so as to open each slit, and define an abutment for an edge of the cutting means so as to sever the ribbon with great accuracy along the slits so that no registration mark remains on the cut labels.
In particular, a preferred embodiment of the invention subject of U.S. Pat. No. 3,435,717 relates to an apparatus in which the ribbon path along which the ribbon is advanced by reciprocating feeding means towards the cutting means is provided, immediately upstream from the cutting means with a centrally located protuberance which urges the central portion of the ribbon away from the ribbon path, whereas the lateral portions of the ribbon are made to advance in contact with the ribbon path by lateral guide means. Said protuberance and guide means cause the ribbon to bow; in particular when a slit leaves said protuberance, its leading edge snaps back into contact with the ribbon path, whereas its trailing edge remains bowed and abuts a lateral side of a knife or movable blade of the cutting means. Positive registration contact between said movable blade and said trailing edge is assured by the feeding means continuing their feeding stroke after the above contact occurs, thus causing the length of the ribbon comprised between said feeding means and the movable blade to buckle longitudinally. Accordingly the movable blade, when operated towards a fixed blade arranged on the other side of the ribbon path, severs the ribbon exactly along the above slit.
The apparatus described in U.S. Pat. No. 3,434,717 is very effective when used to supply with labels or coupons a wrapping device capable of wrapping one or two cigarette packets per second, but is completely unsuited for use with modern wrapping machines capable of wrapping cigarette packets at a normal rate of seven packets per second.
The above will become apparent when considering the operation of the above apparatus at a speed three-four times higher than its normal speed of operation. It is abvious in fact that, since contact between the trailing edge of a split and the movable blade occurs at relatively high speed during the feeding stroke of the feeding means, the shorter the feeding cycle, the higher the speed of movement, the more dangerous the collision between said trailing edge and the movable blade. At a speed three-four times higher than normal, said trailing edge, when abutting the movable blade may either collapse, or bound back.
In either case, the operation of the movable blade may result in the ribbon being severed along a line which does not coincide with the slit.
A further factor which may play a very important role in preventing the exact registration of said trailing edge on said cutting plane consists in that the registering member, that is the movable blade, is moved after registration in contact with said trailing edge and in a direction at right angles to the feeding direction of the ribbon. Since the said trailing edge exerts a pressure on the lateral side of the blade whilst the latter is moved towards the ribbon path, the ribbon may be bent at said trailing edge and thus advance beyond the registered position.